Automatic telephone system.



A. H. DYSON. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED DEC-10,19l0.

Patented NOV. 21, 1916.

6 SHEETS-SHEET 1- fimdfm i fig;

Hffurzzeg Q o 0 I g u I E A A. H.'DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPUCAHON FILED DEC. 10, 1910.

1,205,943. Patented Nov. 21, 1916.

6 SHEETS-SHEET 2.

fiqZParii A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APYLICATION man DEC. I0. 1910.

1,205,943. Patented EW- 21, 19.16,.

A. H. DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED DEC. l0, 19m.

1 05,943. Patented Nov. 21, 1916.

6 SHEETS-SHEET 4 M FZfradHflysan Him/"hay.

A. H. DYSON. AUTOMATIC TELEPHONE SYSTEM. APPLICATIION FILED 050.10. 1910.

1,205,943. E Patented Nov. 21, 1916.

6 SHEETS-SHEET 5.

A. H.- DYSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION men 050.10. 1910.

1,205,943. I Patented Nov. 21, 1916.

6 SHEETSSHEET s.

fi z

UNITED ATE TENT oFFroE.

ALFRED H. DYSON, OF CHICAGO, ILLINOIS, ASSIGNOR T0 KELLOGG SWITCI'IBOARD & SUPPLY COMPANY, OF CHICAGO, ILLINOIS, CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent. Patented N 21, 1916 Applicationfiled December 10, 1910. Serial No. 596,652.

To all whom it may concern:

Be it known that I, ALFRED H. DYSON, a. citizen of the United States of America, residing in Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification My invention relates to automatic tele phone systems of the two wire or metallic line type in which directively controlled switches at the exchange are operated responsive to a series of rapid interruptions of the subscribers line circuits, and without the use of any ground connection at the substations, and to such systems as above outlined, in which upon initiation of a call, a line switch associated with the calling line, automatically extends the circuit of the callling line to an idle directively controlled switch.

An object of my invention is to provide such a system as above outlined, having im-' proved and simplified circuit arrangements, another object being to reduce the number of relays or magnets used on the line switch, one of the features of my invention being the provision of'an electromagnet operating as a cut ofi relay and release magnet.

Referrin to the accompan ins! drawin sin which like reference characters indicate like parts, Figure 1 which includes part 1, part 2 and part 3, illustrates diagrammatically an automatic telephone svstem embodying my invention. Fig. 2 illustrates a line switch adapted to be used in connection with the line switch circuit B, ig. 1, part1. Figs. 3, 4L and 5 are front and side elevations respectively of a selector or connector switch, adapted for use with the circuits or my invention. Fig. 6 is a plan view of Fig. 3 showing more particularly the off normal spring arrangement. Fig. 7 is a cross section of Fig.3 along the line 77 as indi cated on said Fig. 3. Fig. 8 illustrates a modification of the line switch circuit B of Fig. 1 part 1. Fig. 9 illustrates a line switch adapted for use in connection with the line switch circuit B of Fig. 8. Fig. 10 illustrates diagrammatically a modification of the line switch B and first selector switch C of the system of Fig. 1.

Referring now more particularly to the system as shown in Fig. 1 the sub-station A comprises the usual switch-hook and substation equipment, and includes'a calling device. The said sub-station A is connected by means or" the two line limbs as shown, to a line switch B at the exchange. The said line switch B is adapted, upon the initiation of a call from sub-station A, to automatically connect with an idle first selector C as shown in Fig. 1, part 2. The subscriber at A, by the use of the calling device in connection with his sub-station equipment, may by its actuation, operate the first selector C to extend the connection from the said substation A to an idle connector switch D. The subscriber at A then, may by further actuation of his calling device, operate the connector switch I) to connect with the terminals of the called for line E. If the called line is idle ringing current is automatically applied to the terminals thereof to signal the called for subscriber. Should the line of the called for subscriber be busy a characteristic busy signal will be automatically transmitted back to the calling subscriber who may by replacing his receiver upon its switch hook release the switches which were used in extending his line to the line 0]": the called for subscriber. If a connection has been completed for conversation between a calling and called subscriber, the calling subscriber controls the release of the line switch and first selector and the release of the'connecting switch D is controlled by the called subscriber.

The system as illustrated in Fig. 1 is adapted for use as a thousand line system but by the addition of second selectors or third selectors as illustrated in my application Serial No. 586,817, filed October 11, 1910 the system may be increased to any desired size,

General description ofsj stem Fig. 1.-- The equipment of sub-station A comprises the usual switch hook 1, which normally closes a circuit through call bell 2 and condenser 3, and which is adapted, upon the removal of receiver a therefrom to open the lower contacts, thereby disconnecting the call bell and by closing the upper contacts,

connecting in circuit, transmitter 5, impedance coil 6 and the impulse contact springs 8 of calling device Impedance COll 6 also serves as a. magnet to unlock the dial of calling device 7, as will be here1nafter more fully explained. To operate calling device 7, to transmit a certain predetermined number of impulses, the operator rotates the dial in a clock-wise direction until a number of insulated projections corresponding to the number of impulses to be transmitted have passed impulse spring 8v but it will be noted that when the dial is advanced the contact springs do not open. The operator then releases the dial which is restored by the spring shown thereon, thereby opening'and closing impulse springs 8 the proper number of times. Shunt springs 9 are adapted to be closed while the dial is off normal, thus shunting, the winding of coil 6 and reducing the line resist ance. 7 means of line limbs 10 and 11 to terminals of relay COR ofline switch B.

The line switch B comprises a line relay LR- which is adapted, upon initiation of a call from sub-station- A, to automatically start travel of the wipers of line switch B responsive to operation of motor magnet MM, to connect with the terminals of an idle first selector C. Magnet COR of switch B serves as a cutoff relay for the said switch, being adapted upon energization to remove the sub-station control of the line relay LR and also to extend the line conductors of substation A to the selected first selector C. The said magnet COR also serves as a release magnet for line switch B, being; adapted upon deenergization, to allow the restoration of the wipers of the line switch B. Off normal switch ON is adapted tobe moved to its alternate position upon the first step ofthe wipers of line switch B, and to be restored upon restoration of the said wipers. Switch springs 12v and 13 are controlled by magnet COR, the operation of which will be-more fully explained.

Terminals 1%, 15 and 16- are the multiply connected terminals of the connector switches having access to the line of the substation A.

lVipers 17, 18 and 19 of line switch B are adapted to connect with contacts 20, 21 and leading to first selectors such as .C. Each sub-station line in the exchange has a line switch B, which by means of wipers 17. 18 and- 19 have access to a plurality of first selectors C, preferably ten in number, although the number of first selectors C to which a linehas access may be varied to suit existing conditions. The sub-station lines and line switches B are divided into groups of one hundred, and there are ten first selectors C for each group of one hundred lines, therefore on a basis of ten per cent. trunking which is sufiicient for ordinary purposes, each subscribers line switch B would have access to ten. first selectors C. Each first selector C is multiply connected to the terminals 20, 21 and of 100 line nections are shown.

The substation A is connected by' Each first selector 0' comprises impulse relays IR and IR which are adapted to be bridged across the line of a calling subscriber. Said relays IR and IR are controlled over a metallic circuit of a calling subscribers line, being adapted to be operated by interruptions of the metallic circuit in which they are included by means of a subscribers calling device. Primary magnet PM is adapted responsive to current impulses from the impulse relays, to move wipers 23, 24, in a primary direction to select a group of bank contacts 26,. 27, 28 leading to connector switches D. Secondary relay which is shown as a sluggishv or slow acting relay, is adapted to transmit a secondary impulse after the primary impulses have been transmitted, to energize busy relay BR which controls the selection of an idle trunk. The energization of busy relay BR closes a circuit through secondary magnet SW which causes a secondary move ment of wipers 23, 24: and 25 along the selected row or group of contacts. Main release relay MRR is a slow acting relay directly under control of a calling subscriber, which controls the release of certain switches, as will hereinafter be more fully explained. Release relay RR controls the operation of release magnet R-M which is adapted upon energization to restore wipers 23 21 and 25 to normal. Primary off normal switch. PON is adapted to be moved to its alternate position upon the first primary movement of wipers 23, 21 and 25, and. secondary off normal switch SON is adapted to be moved to its alternate position upon the first secondary movementof wipers23, 2e and 25. The ofi normal switches are restored to normal upon restoration of said wipers 23, 2% and 25 from their respective movements. The wipers 23, 2e and 25 of each first selector are adapted to be connected with terminals 26, 27 and 28- of one hundred connector switches D, divided into ten groups. there being ten such connector switches D for each group of one hundred lines in the exchange. Each connector switch is multipled connected to bank contacts 26, 27 and 28 of one hundred first selectors C. Therefore, each first selector (3 has access to ten connectors D in each group of one hundred lines in the exchange.

Each connector switch D includes a primary magnet PM" which is adapted to move wipers 29, 30 and 31 in a primary direction to any one of ten groups of bank contacts 32, 33 and 3st. Secondary magnet SM" is adapted to move the said wipers 29, 30 and 31 in a secondary direction to connect with oneof the sets of contacts 32, 33 and 34 in the selected group. Switch relay SlV is adapted to disconnect primary magnet PM and connect secondary magnet SM with the primary or upper heavily marked conductor of connector switch D. Release relay RR is adapted to control the operation of release magnet RM to release the wipers of connector switch D. Test relay TB is adapted to be connected to the private or busy terminal 32 of the called line to test its idle or busy condition, so if idle, ringing current may be applied or a characteristic busy signal from busy back BB may be transmitted to the calling subscriber if the called for line is busy.

Interrupter wheels I and I are preferably mounted upon the same shaft in the relative positions shown and are rotated in a clock-wise direction by any suitable motive power. The line switch B of the called for subscriber at E is similar to line switch B of the calling subscriber at A, although a portion of the said switch circuit B is not illustrated. The requirement of substation E is similar to that of sub-station A.

Referring now to Fig. 2 the switch structure there illustrated is adapted to operate in connection with the circuit of line switch B. The switch of Fig. 2 comprises a main mounting plate 35, to which is secured the contact bank 36. The said bank includes a pair of clamping plates 37 firmly clamping ten sets of bank contacts 20, 21, and 22,

suitably insulated from each other. Vipers V 17, 18 and 19 which are adapted to cooperate with said bank contacts are suitably secured to shaft 38, the said shaft 38 being journaled in plate 35 and bracket 39. Vipers 18 and 19 are adapted to cooperate with contacts 21 and 22 respectively when shaft 38 is rotated and wiper 17 which is the middle wiper is adapted to cooperate with the contacts 20. The ends or contacting portions of wipers 21 and 22 are so formed that when moving from one set of contacts to another in the bank, they will break contact with one set before making contact with the next set. l/Viper 17 has its end or contacting portion so formed that when being advanced along the row of contacts, it makes connection with one contact 26 before breaking connection from the contact it is leaving. Ratchet wheel 40 is rigidly secured to shaft 38 as is also the arm 41. Detent 42 which is pivoted at an interme diate point, normally rests under tension of spring 42 against ratchet wheel 40, and is adapted to prevent restoration of wipers 17 18 and 19 until said detent is withdrawn from engagement with said ratchet wheel 40. Motor magnet MM which is suitably mounted on plate 35 has an armature 43, carrying a pawl 44, pivoted to said armature 4-3 by means of pin 45. Pawl 44 is shown in its normal position with its upwardly extending portion 44" resting against the adiustable stop screw 46. Tension spring 47 is secured to armature 43 and is adapted to press pawl 44 into en-- gagement with ratchet wheel 40 upon attraction of armature 43. As armature 43 is attracted, pawl. 44 is moved toward the left and as it tends to move away from step screw 46, spring 47 moves it upward into engagement with ratchet wheel 40 and the armature continuing in its movement, pawl 44 rotates ratchet wheel 40 stepping the wipers into engagement with the first set of bank contacts. Upon each deenergization and energization of magnet MM the wipers are advanced one step moving from one contact to the next along the row. Rod 48 which is preferably square is carried in suitable openings in bracket 49, the said rod 48 being adapted to reciprocate in its bearings, but due to its square shape is not rotatable. The pin 48 in rod 48 due to its engagement with bracket 49 serves as a stop for wiper shaft 38 upon its restoration, due to the engagement of arm 41 with the said rod 48. Oif' normal springs ON rest under tension against member 48", the said member being rigidly secured to red 48. Thus when the wiper shaft is moved off normal, arm 41 moves'away from red 48, allowing oil normal springs ON to move the rod 48 downward, the said springs thus assuming an alternate position. Excessive movement of rod 48 is prevented by step pin 48 engaging the uppersurface of the lower extension of bracket 49. Magnet COR which serves as a cutoff relay and release magnet, has an armature 50 pivoted to pole piece 51. Fastened to the said armature 50 is the release catch 52 normally resting under tension against the upper end of rod 48. Said release catch has two holes 54 and 55 therein, which are adapted upon energization of magnet CUR to drop over the upper ends of detent 42 and piv oted arm 53. Springs 12 of which the lower one rests under tension against release catch 52, are adapted to have their contacts broken when the release catch drops downward over the ends of detent 42 and arm 53.

It will be noted that when wiper shaft 38 moves off normal and rod 48 moves downward release catch 52 rests on the upper end of arm 53, but the springs 12 are so adjusted that this slight movement of catch 52 does not open their contact. Upon energization of magnet CUR, after wiper shaft 38 has moved ofl" normal, the openings of 54 and 55 of catch 52 drop downward over the ends of detent 42 and arm 53 and upon deenergization of magnet COR the said catch 52 moves the upper ends of de tent 42 and arm 53 to the left, thereby moving detent 42 out of engagement with ratchet wheel 40, and opening the contacts between springs 13 by means of arm he operation of line switch Fig. 2 is as follows: When the motor magnet MM is energized and deenergized, pawl 44 engages the teeth of ratchet wheel thus advancing wipers 1'7, 18 and 19 along the row of contacts 20, 21 and 22, each energization and deenergization of the said magnet advanc ing the said wipers one step, or the distance from one set of contacts to the next. Upon the first morement of wiper shaft 38 off normal, arm t1 which is carried thereby, moves downward, thus allowing oif normal springs Oi to assume an alternate position and also moving rod i8 downward thereby allowing spring member 52 to rest on the upper end of pivoted arm 53. The magnet COR is now energized and upon complete attraction of its arn ature the openings 5% and in release catch 52 are in a position to drop down orer the ends of detent and arm The downward movement of said release catch allows contact springs 12- to assume an alternate position. To release the switch magnet COR is dei nergized retracting the armature 50, thus moving the upper ends of detent a2 and arm 53 toward the left. The movement of arm 53 moves the upper spring 13 out of engagement with its lower contact spring. Detent :2 being pivoted at its central portion, has its lower end moved out of engagement with ratchet wheel l0 and the wipers 17, 18 and 19 are restored to normal by means of the spring shown in connection with ratchet wheel 40. Upon restoration of the wipers, arm 41 engages rod l8 moving it upward until pin 48' engages the lower surface of bracket i9. The restoration of rod 18 restores ofi' normal springs 3N and the upper end of rod 48 engages catch lifting it out of engagement with detent and arm 53, allowing the said detent and arm to be restored. The upward movement of catch 52 restores contact springs 12 to normal and the restoration of arm by the upper contact spring 13. allows the said contact spring .13 to assume its normal position in engagement with its lower contact. Upon restoration of detent -l2 into engagement with ratchet wheel l0, the switch of 2 is again at normal.

Selector and C07l-77.@( Z 07 switch construction-.Referring to the switch illustrated in Figs. 3 to 7, the said switch is adapted to be used either as a selector or a connector switch by arranging the off normal springs, as illustrated in the difl'erent circuit diagrams.

The switch illustrated comprises a frame (30, on which are mounted the different actuating magnets. Secured to the lower and back parts of the frame 60. is the bank contact frame comprising the upper member 61 and lower member 62. he said members are connected by posts 63, which are adapted to clamp ten banlrs of contacts such as 64-. Each contact bank 6%, comprises two clamping plates 65 which are adapted to hold ten are one hundred sets, is represented by a single short line, having been illustrated in this manner, believing the drawing will be more readily understood. The ten contact banks (54: are radially disposed between the clamping plates 61 and 62 so spaced that the wipers Ql, when rotated by the primary shaft PS are stepped along from one contact bank to the next. The primary shaft PS is journaled in the upper and lower horizontal extensions of frame 60 and is adapted to partake of rotary motion only. .lt will be noticed said shaft is broken, the upper portion being at normal and the lower end carrying the wipers being in a position so that the wipers are below the fifth contact bank. The plate 67 is secured to primary shaft PS by the pivot 68 and wipers 2 t, 25, are secured to the lower end of said plate 67 and are suitably insulated therefrom. The upper end of plate 67 has fastened to its sides the forked retaining members (59, which are adapted to secure the roller 70 to plate 67. The roller 70 has a slot through its center, which is adapted to receive the horizontal portion of member 71, the said member 71 being loose within the slot of roller 70 so that when shaft PS is rotated slotted roller 70 slides along plate 71. Primary ratchet 72 is suitably fastened to primary shaft PS. The restoring spring 73 is disposed about the primary shaft PS having its upper end secured to the horizontal extension of frame 60 and its lower end secured to the hub of primary ratchet 72. Fastened to the upper end of primary shaft PS is the hub 74.- carrying the stop arm 75 and the forwardly eX- tending arm 76. Stop arm 75 normally rests against its engaging stop pin, thus holding the primary shaft PS in its normal position under tension of spring 73. Secured to the end of arm 7 6 is the insulated stud 77 which is adapted upon the first movement of primary shaft PS, to move in a cloclewise direction away from the primary off-normal springs PON, thus allowing them to move to their alternate position. Primary magnet PM, which is adapted to rotate primary shaft PS thus giving the wipers 23, 2%, 25, their primary movement, has an armature 78, suitably pivoted to its pole piece. The said armature 78 carries a pivoted pawl 7 9 adapted to cooperate with primary ratchet 72. Spring 8l,which is suitably secured to armature 78 has a free end resting against the leftfront portion of pawl 79. The adjustable stop screw 82 acts as a stop for armature 78 and also cooperates with pawl 79, thus when armature 78 is attracted moving away from stop 82, the spring 81 rotates pan 1'79 on its pivot 80, thus bringing it into engagement with a tooth of ratchet 72. The continuation of movement of armature 78 then advances or rotates ratchet 72 until the beveled portion 7 9 of pawl 79 engages the beveled portion of stop 83 and it will be seen that the pawl is thus locked in engagei'nent wit-h a tooth of ratchet wheel 72, preventing any overrun of the primary shaft PS, due to the momentum received from its advance. Retaining pawl 84 is pivotally secured to supporting stud 85. being held. in engagement with ratchet wheel 72 by spring 86.

Secondary shaft SS, which is preferably square is suitably journaled in the horizontal extensions of frame 60 and is adapted to receive rectilinear movement only. At the lower end of shaft SS is the stop 87 normally resting against the lower surface of frame 60. Screws 88 clamp said stop 87 and member 71 against opposite faces of shaft SS, both of the said members 87 and- 71 being adjustable. At the upper left side of shaft SS in Fig. .3 are ratchet teeth 89, the said teeth being adapted to be engaged by pawl 108 of secondary magnet SM. On the right hand. side ofsecondary shaft SS, the teeth 90 are cut. as shown in Fig. 3, the said teeth being engaged by retaining pawl 91 to hold shaft SS in its actuated position. The retaining pawl 91 is pivoted by shaft 92 to the vertical front supporting bar 93. The said pawl 91 is held in engagement with teeth 90 by spring 94. The extension 91 of pawl 91 is adapted to be engaged by the extension 84 of pawl 84- when the said pawl 8411s operated upon release of the switch. The secondary shaft restoring spring 95 is secured at its lower end to stud 96 which is fastened to the frame 60, the upper end of spring 95 being hooked over the lever 97. The lever 97 is adjustably fastened to secondary shaft SS by means of screw-98, the said screw 98 working in the slot shown at the forward end of lever 97. The lever 97 is pivoted to the downward extending bracket 99. The said spring 95 holds secondaryshaft SS in its normal position with stop 87 resting against the lower surface of frame 60. The offnormal plate 100 extends through openings in the upper and lower extensions of frame 60 being arranged alongside of secondary shaft SS. The said plate 100 is loose in the said frame and is adapted to be carried downward when the secondary shaft SS is actuated upon its first movement. At the upper end of bar 100 is an extension 101 having an opening through which secondary shaft SS extendsas shown in Fig. 6. The secondary off-normal springs SON rest under tension on the said extension 101 being held in their normal position thereby. The lower end of plate 100 rests against stop 87 thus when shaft SS is moved downward the springs SON move plate 100 downward until extension 101 rests against the upper surface of the upper extension of frame 60. Upon the restoration of secondary shaft SS, stop 87 again engages the lower end of bar 100 carrying it upward and restoring the springs SON. The small projecting portion or dog 102 of plate 100 is adapted to bemoved into engagement with a tooth of the primary ratchet 72 when the plate 100 is moved downward. This is to prevent undue tension .or pressure against the sides of the bank contacts when the wipers are being restored from their secondary move ment, as will be more fully explained. Secondary magnet SM is mounted on the vertical poition of frame 60 and also secured to the upper horizontal extension 105' of frame 60 at its forward end. Armature 103 of secondarymagnet SM is pivoted at rear plate 101 and front plate 105, the said plates being suitably secured to the core and end pole pieces 106 of'magnet SM. Spring 07 is suitably fastened to plate 105 of magnet SM and has its upper end engaging armature 103. Pawl 108 is pivoted to armature 103 normally resting against the lower surface of extension 105 of plate 105. The said extension 105 serves as a stop for armature 103, also being adapted to move pawl 108 out of engagement with teeth 89 of secondary shaft SS upon each restoration of armature 103. Upon the attraction of armature 103 pawl 108 moves downward and away from stop 105 and by means of spring 109 is rotated on its pivot and into engagement; with teeth 89 of secondary shaft SS. lontinuing it its downward movement pawl 108 moves shaft SS downward until the beveled portion 108 engages the beveled surface of stop 110 and as in the case of the primary ratchet, locking the actuating pawl and preventing any overrun of shaft SS due to the'momentum received from its advancement.

Release magnet RM is rigidly fastened in a suitable manner to the vertical back of frame .60 and has an armature 110 pivoted at the forward end of pole piece 111. The lower end of armature 110 is adapted when attracted to engage the extension 8 1 of primary retaining pawl 81, this moving said pawl out of engagement with primary ratch 72.

Operation of selector 0? connector switch.-Having described in general the construction of the switch illustrated in Figs. 3 to 7, the operation of said switch will now be described. The primary magnet PM is first energized and deenergized attracting and detracting its armature 78 and for each operation of said magnet PM pawl 7 engages primary ratchet 72 advancing the wipers 23. 25 one step in a primary direction continuing to a point opposite the desired bank it will be noticed that the wi ers travel along below the lowest contact set of the contact banks in their primary movement keeping clear of the said bank contacts. Upon the first primary step of the wipers, arm 7 0, which is carried by primary shaft PS and secured to its upper end, moves insulated stud 77 toward the left away from the primary off-normal switch PON allowing said switch to assume an alternate position. The secondary magnet SM is 110w energized and deenergized stepping shaft downward, and the wiper carrying plate (37 being connected to plate 71, the said plate 67 is rotated about its pivot 68 stepping the wipers 23, 25, upward along the row of contacts of the selected bank. Upon the first secondary step of shaft SS stop 87, which is secured to its lower end, moves downward, allowing the secondary off-nor mal springs SOB to move the plate 100 downward until extension 101 rests upon the upper surface of the upper horizontal extension of frame 60. The contact springs of secondary oif-normal switch SON, due to this movement, have assumed their alternate position. ri so. upon the. downward move ment of plate 100. the dog 102 engages a ooth of primary ratchet 72, locking said irimary ratchet until plate 100 is restored.

To release the switch mechanism, release magnet RM is energized attracting its armature 110. which engages extension 8& of pawl 81- rotating said pawl on its pivot and moving it out of engagement with primary ratchet 72. It will be seen that if ratchet 72 were not at this time locked by some auxiliary means, the tension of spring 7 3 would cdiatcly tend to press wipers 23, 25 t the sides of contacts 26 and 28 and cause undue friction while the wipers are restoring from their secondary movement.

It will be remembered that dog 102 has engaged a tooth of ratchet wheel 72, thus preventing this undue pressure against the sides of the bank contacts until said dog has been released from its engagement with the ratchet wheel '72, which does not occur until the secondary shaft SS reaches normal.

Returning now to the operation of the release magnet, the armature 102- ha ing disengaged pawl 81 from ratchet wheel 7 2, the extension 81 engages extension 91 of secondary pawl 91, moving it away from shaft SS and disengaging the said pawl 91 from the teeth 90 of secondary shaft SS. The primary sl at PS being locked by dog 102, the secondary shaft SS will be the first to restore, this being effected by the restoring spring 95 which acts upon secondary shaft SS through lever 97. Secondary shaft SS now moves upward thus restoring wipers 23, 24, 25 from the secondary movement. the shaft continuing upward until block 87 engages the lower surface of frame 60. The upward movement of block 87 also restores plate 100, thus disengaging dog 102 from ratchet 72 and restoring the secondary oil'- normal switch SON. As soon as dog 102 disengages from ratchet wheel 72 the restoring spring 73 acts upon primary shaft PS, restoring wipers 21, 25 from their primary movement until the arm 75, which is secured to the upper end of shaft PS, engages its stop pin. The restoration of shaft PS also causes the restoration of the primary off-normal switch, due to the engagement of said switch by the insulated stud 77, which is carried by arm 76. The switch and all its associated mechanism is now at normal.

Operation of system Fig. .Z.-Ha ing dcscribed in general some of the relays and switch contact springs of the system of Fig. 1 and the switches used in connection therewith, the operation of the said system in completing a connection from a calling to :1 called subscriber will now be described.

Assuming that the subscriber at sub-station A desires to connect with a subscriber at sub-station E whose number we will assume is 234, the subscriber at A removes rereceiver 1 from its switch hook 1, allowing said. switch hook to move upward and close connection with the upper contacts. A circuit for the line relay LR is thereby established, traced from ground at normal contact 120 of relay COR, line limb 11, transmitter 5, switch hook 1, and contact 1, contacts 8, winding of coil 6, line limb 10. alternate contact 121, off-normal contact ON through the winding of line relay LR to battery, energizing the said relay. Responsive to the said energization, a circuit for motor magnet MM is established from ground through alternate contact 122 and the winding of motor magnet MM to alternating current generator. The said magnet MM is thereupon energized advancing wipers 17, 18, 19, engaging respectively with the first set of contacts 20, 21, and 22, which are connected to a first selector C. On the first. step of wipers 17 18 and 19, off-normal switch ON is moved to its alternate position thereby opening the initial energizing circuit for relay LR. Assuming that the first selector switch with which contacts 17, 18 and 19 connect is busy, there will be a ground upon private contact 20 and a locking circuit for relay LR will be established from the said ground over wiper 17, switch contact 13, through alternate contact 123 and winding of relay LE to battery. The motor magnet thereupon advances wipers 17, 18 and 19 another step and if the second set of contacts lead to a busy first selector switch, line relay LR remains energized and motor magnet MM continues to advance wipers 17,

'tery energizing said relay.

18 and 19 until an idle set of contacts 20, 21 and 22, are connected with. Assuming that switch G of Fig.- 1, part 2, is the idle switch connected with, there will be no ground upon contact 20 and the locking circuit for delay LR being interrupted its armature will retract opening the energizing circuit for motor magnet MM, thus preventing any further advance of the wipers 17, 18 and 19. Upon the deenergization of relay LR a circuit for impulse relay IR of switch C is established from ground at normal contact 122 through normal contact 12, normal contact 124, talking conductor S, wiper 19 and bank contact through the winding of .relay IR to battery, energizing the said relay. Responsive to the energization of relay IR a circuit for relay 125 is established from ground through alternate contact 126 of relay IR, normal contact 127, normal. contact 128, through the winding of relay to bat- Responsire to energization of relay 125, an energizing cir cuit is established for relay IR from battery through the winding of relay IR. conductor 129, alternate contact 130, conductor 131. and winding ojl' relay IR to ground energizing said relay IR. Also, upon energizatlon of relay 125 a circuit for cut-off relay COR is established from ground through alternate contact 132, contact 183, bank contact 20, wiper 17, switch contact 13, normal contact 123 and the winding of said cut-off relay COR to battery, energizing said relay COR.

Returning now to relay IR. Upon its energization a circuit for main release relay MRR is established through alternate contact 134 and winding of relay MRR to bat tery; Relay MRR is thereupon energized establishing a new locking circuit for relay COR from ground at contact 135. The resistance which is connected between ground and contact 135 is for the purpose of reducing the current consumption of the cut-off relay COR, as the said relay remains energized until the calling subscriber restores his receiver to its switch-hook. Upon the energization of relay MRR the energizing circuit for relay 125 is opened at contact 128 thus allowing relay 125 to restore and open the initial energizing circuit for relay IR, at contact 130. But the relay COR having beenenergized before relay 125 retracted its armature, a new path for energizing relays IR and IR was established, the said circuit being traced as follows: from battery through the winding of relay IR, bank contact wiper 19, alternate contact 121, line limb 10, through the sub-station A, returning over line limb 11, alternate contact 120, wiper 18, bank contact 21, and the Winding of relay IR to ground. The said ground from contact 135 also renders all multiples of private contact 20 busy, preventing other line switches from connecting with switch G.

The line of the calling subscriber at A has now been extended to the first selector C, and relays IR and IR are energized over the path just traced including sub-station A. This pathincludes the winding of magnet 6 which is energized by the current in said patlnthereby unlocking calling device 7. The subscriber at sub-stationA now revolves the dial 7 until two insulated projections have passed impulse springs 8; The subscriber then releases the dial. and it is restored, opening and closing impulse springs 8 two times. The opening and closing of the said impulsesprings 8 causes two interruptions t the previously described circuit of relays IR and IR, and tl ey retract and attract their armatures two times. Responsiveto the operations of the said relays IR and IR two current impulses are transmitted through primary magnet PM and two current impulses are transmitted through sec ondary relay SR. Although when relay IR is operated, the circuit through relay MRR is interrupted, said relay MRR being sluggish or slow acting, does not retract its armature until its circuit is interrupted for a comparatively long interval. dei' nergization of relay IR the first current impulse through relay SR is established from ground through normal contact 126, alternate contact 136 of relay MRR which is maintained actuated, and the winding of relay SR to battery energizing relay SR. Relay IRv is again immediately energized thus opening this circuit, but relay SR being a slow acting relay, it will be seen that it re tains its armature in an attracted position while the circuit of relay IR is being in terrupted. The impulses which operate primary magnet PM are traced from ground through normal contact 1341 of relay IR, alternate contact 137, conductor P, normal contact 138, through the winding of said n-agnet PM to battery. For each current impulse transmitted from ground at normal contact 134, the primary magnet PM advances wipers 2 3, 2d, 25, one step in a pri mary direction and, as previously stated,

the subscriber having caused two interrup tiens of the energizing circuit for relays IR and IR, the wipers 23, 24, 25 are stepped to a point adjacent the second group of bank contacts, which are the contacts leading to connector switches D, which have access to the one hundred line group with which the line of the calling subscriber B is associated.

After he last interruption of the circuit for relays IR and IR, the said relays remain energized and relay SR has its energizing circuit open long enough at normal contact 126 to allow it to retract its armature. Responsive thereto, a circuit for busy relay BR is established from ground at normal contact 139 of relay SR, conductor S, conductor 140, normal contact 141 of switch Upon the first lay BR, normal contact 144, through winding of secondary magnet SM to alternating current generator. Responsive to current from the said generator, secondary magnet Sill steps wipers 23, 24:, and 25 into engagement with the first set of contacts 26, 27 and 28 of the selected group. Upon the first secondary step of wipers 23, 24*, 25, switch SON moves to its alternate position thereby disconnecting primary na- 'net PM from conductor P and by means of contact 1 11 opening the initial energizing circuit for 'relay BR.

hiss-inning that the first set of contacts, 26. 28, with which wipers 23, 2-l, and 25 have connected lead to a busy connector switch D, there will be a ground upon contactQG as will be hereinafter described, .and locking circuit for relay BB. is established from the said ground through wiper 23, normal contact 1 1-5, normal contact 146, through alternate contact 147 and the winding of relay BP to battery. The energizing circuit for magnet S11 is therefore maintai-ned and its armature is again attracted advancing wipers 2%, into engagement with the next set of contacts. Thus, it will be seen that as long as wiper 23 is engaging grounded bank contacts 26 leading to busy connector switches, the busy relay BB is maintained energized and magnet SM continues to advance wipers 23, 2-l, 25. Assuming now that the connector switch D illustrated in Fig. 1, part 3, is the first idle one ot the groug, upon connection with its private cont-act 26 by wiper 2, the locking circuit for r lay BB is interrupted and the said relay retracts its armature thus opening the circuit for magnet Slil and preventing any further advance of the wipers 23, 24, 25. l pon d l ner, ration of relay DR a busy or ground condition is placed upon bank contact 2'3 and all of its multiples to prevent the said connector switch D from being selected by any other selector switch. This ground connection is traced from ground at normal contact 1&7 of relay BR, normal contact 1&6, normal contact 1 15, and Wiper 23 to bank contacts 26. The line of the calling subscriber has now been extended to the terminals 2G, 27 28 leading to connector switch D. The subscriber at A now operates calling device 7 to cause three interruptions of the energizing circuit for relays IR and IR. Responsive to the said interruption impulses are transmitted through secondary relay SR which again maintains its armature attracted until after the last impulse of the set has been transmitted, as previously described. Responsive to the three interruptions of the circuit of relay IR, three impulses are transmitted from ground through its normal contact 134, alternate contact 137, conductor P, normal contact 14:8, wiper 24:, bank contact 27, conductor P, normal contact 149, normal contact 150 of switching relay Sll. through the winding of primary magnet PM to battery. Responsive to the said three impulses, primary magnet PM steps wipers 29, 30 and 31 to a point adjacent the third group of ten bank contacts or line terminals with which the line terminals of the called for sub-station E is associated.

After the last impulse has been transmitted from relays IR and IR the secondary relay SR retracts its armature as before and a secondary impulse is transmitted from ground through its normal contact 139, normal contact 151, wiper 25, bank contact 28, conductor S, alternate contact of switch PON, which closed upon the first primary movement of wipers 29, 30 and 31, through the winding of switching relay SlV to battery. Switching relay SW is thereupon energized and by means of contact 150, primary magnet PM is disconnected and the secondary magnet SM is connected to conductor P. A locking circuit for relay SW is also established upon its energization from ground at normal contact 153 of release relay RR, through alternate contact 15% of relay SlV to battery. The calling subscriber at sub-station A now operates the calling device 7 to interrupt the circuits of relays IR and IR four times. Responsive to the said interruptions four impulses are trans-.

mitted from relay IR through secondary relay SR, thus maintaining the armature of said relay SR attracted while the impulses are being transmitted, as previously described.

Due to the four interruptions of the energizing circuit for relay IR, four impulses are transmitted through the secondary magnet SM of connecter switch D, being traced as follows: from ground through normal contact 134: of relay IR, alternate contact 137, wiper 2%. bank contact 27, conductor P of connector D, normal contact 149, alternate contact 150 of switching relay SW, through the winding of secondary magnet SM to battery. Responsive to the said four current impulses, secondary magnet SM operates its armature four times stepping wipers 29, 30 and 31 in a secondary direction into engagement with the fourth set of contacts in the selected group which are contacts 32, 33, and 3a and are the terminals of the line of the called for substation E.

Afterthe last one of the four primary im pulse is transmitted from relay SR as previously described, energizing relay SR of connector switch I) over a path traced from ground through normal contact 139 ofrelay SR, wiper 25, bank contact 28, oii'normal switch SON which closed upon the first secondary movement of wipers 29, 30

and 31, through normal contact 155 and winding of relay SR to battery. Relay SR is thereupon energized and a circuit for relay 156 is established from ground at normal contact 153, conductor 157, through alternate contact 158 ofrelay SR and the winding ofrelay 156 to battery. Relay 156 is thereupon energized and a locking circuit therefor is established from the same ground at normal contact 153, through a1- ternate contact 159 and the winding of relay 156 to battery. Also, upon energizationof relay SR the test relay TB is connected to the private wiper 29, the said connection being established over the following path: from said relay TR through norn'ial' contact 160, alternate contact 161 of relay SR to wiper 29.

Ualled Zinc idZe.-The operation 01" the switches up to the point just described is the same whether connected to an idle or a busy line, but from this point on the operation is different when connecting to an idle or a busy line. Assuming that the line of the called for subscriber is idle, therewill be no ground or busy condition upon its private contact 32, and the test relay TRwhich was connected to the said contact 32 upon the energization of relay SR, does not attract its armature as the connection is from battery to battery. It will be remembered that relay 156 became energized as soon as contact 158 of relay SR closed and upon energization of said relay 156 the energizing circuit for secondary relay SR" was interrupted at contact 155 of relay 156. Therefore, secondary relay SR deenergized retracting its armature and disconnecting test relay TR from wiper 29. Upon the said deenergization of relay SR, ringing control relay RCR is connected to wiper 29 and a series energizing circuit for said relay RCR and cut-ofl' relay COR is established from ground through the winding of said relay RCR, alternate contact 162, normal contact 161, wiper 29, bank contact 32, normal contact 123 and the winding of relay COR to battery. The ringing control relay ROB and the cut-off relay COR are thereupon energized, the energization of the cut-off relay removing the substation control of line relay LR. The private contact 32 now being grounded through the winding of relay R-CR, the multiplecbank contacts are of course grounded and thereby prevent any other connector from connecting any other calling subscriber with the subscriber at A.

Responsive to the energization oi relay of the switch hook returning over line limb 11, contact 33, wiper 30, conductor 173, alternate contact 174:, impedance coil 175 and through battery to ground. The interrupter wheels I and I are being revolved in a clock-wise direction and generator G is disconnected as soon as the insulation strip of wheel 1 comes into contact with its brush. The wheels continue in their movement, the upper half of wheel I connecting ground to the alternate contact 17 2. At this time relay 167 is still connected to battery through the live segment of interrupter wheel I and ground being connected to alternate contact 172 from the grounded segment of wheel 1, any charge which the line or condenser of the called for subscriber may accumulate from the ringing current, is dischar ed through the said ground connection. This ground connection with the segment of wheel I is only momentary, as the interrupter wheels continuing in their movement, the energizing circuit for relay 167 is interrupted as soon as the dead segment of wheel I connects with its brush and it retracts its armature.

Upon deenergization of relay 167, control relay GR, is connected to the line oi the called for subscriber, the said. connection being traced from ground. through the winding of said relay CR, alternate contact 17 6, ncrmalcontact 172, wiper 3.1 to bank con tact 34 and line limb 10. The other line limb 11 is connected to battery through impedance coil 175, as previously described, but the subscriber not having responded as yet, condenser 3 prevents a flow of current from the battery at impedance coil 175 out over the line and back through control relay CR to ground. Thus it will be seen that the interrupter wheels I and I continue to revolve, alternately connecting generator G and control relay CR to wiper 31 and terminal 3d of the called for subscribers line. The subscriber now responding to the call, removes his receiver from its switch hook and as soon as relay 167 deenergizes acircuit for control relay GR is established from ground through the winding of said relay CR, alternate contact 176, normal contact 172, wiper 31, bank contact 3 1, line limb 10, sub-station E and line limb 11, contact 33, wiper 30, conductor 173, alternate contact 17%, impedance coil 175 to battery. Control relay CR is thereupon energized and is now under the control of the called for subscriber, as its energizing circuit is established over the line limbs and through the sub-station E.

Responsive to the energization of relay CR, talking control relay TC is energized over a path t aeed from ground at normal contact 153 or relay RR, conductor 157, conductor 16S, alternate contact 169, alternate contact 177 through the winding of said relay TC to battery. Upon the energization of relay TC, the circuit of relay 167 is interrupted at contact 171 of relay TC, thus rendering relay 167 inert and preventing any further application of ringing current to called line. Also upon energization of relay TC, a ground connection to private contact 20 is established from ground at alternate contact 178 of relay CR, alternate contact 179, relay TC to contact 26. This ground connection is for the purpose of shunting release relay RR after the called for subscriber has responded, thus preventing the release of connector switch D by the calling subscriber and rendering the release of the said switch under the control of the called for subscriber. Also, responsive to energization of relay TC, alternate contacts 180, and 181 are closed, thus establishing the continuity of the talking circuit connecting the calling and called subscriber, which is traced along the heavily marked conductors and in which are interposed the condensers 182 and 183 at first selector switch C. The sub-stations are now connected in a conversational circuit, talking current for the ealling subscriber is supplied over the previously traced path including relays IR and IR and talking current for the called sub scriber is supplied from battery through inipedance coil 175 returning through control relay CR to ground over the previously described path.

Release of completed connection Fag. Assuming now that the subscribers have finished conversation, by replacing their receivers upon their respective switch hooks. the switches which were used in establishing the connection will be released. In this instance the release of the line switch B and first selector C is under the control of the calling subscriber and the release of the connector switch D is under the control of the called subscriber. Assuming now that the subscriber at A be the first to replace his receiver upon its switch hook. the previously described energizing circuit for impulse re lays IR and IR, is interrupted at the upper contacts of switch hook 1. The said relays IR and IR are thereupon deenergized, restoring their contacts to normal and interrupting the circuit for the main release re lay MRR, at alternate contact 134 of relay IR. Main release relay MRR is thereupon deenergized restoring its contacts to normal and establishing an energizing circuit for release relay RR, traced from ground through normal contact 126 of relay IR, normal contact 136, alternate contact 142 of switch PON, through the winding of release relay RR to battery. Relay RR is thereupon energized, attracting its armature and closing a circuit from battery through the winding of said relay BR, alternate contact 181- to the ground connection which is established from relay IR for energizing relay RR. Relay ER is energized responsive to the said established circuit thus opening the connections from wipers 2st and at contacts 1&8 and 151. Responsive to the energization of release relay RR, alternate contact 14-6 conneets battery to wiper 23, but this has no effect upon connector switch D at this time as it will be remembered that private contact 26 is connected to ground at alternate contact 178 of relay CR, thus shunting relay RR of connector D.

Returning now to relay BR, upon its ener gization, a circuit for release magnet RM is established from ground, through alternate contact 143, alternate contact 144, through winding of release magnet RM to battery, ener izing said magnet. Upon energization of the said release magnet, the retaining pawls holding wipers 24, 25 in connection with contacts 2G, 27, and 28 is withdrawn allowing the Stilt wipers to be restored to normal. Upon restoration of the wipers, secondary oft-normal switch SON is first restored to its normal position and thereafter primary oil-normal switch PCN is restored to normal as previously de scribed. Upon restoration of switch PON, the energizing circuit for relays RE and BB is interrupted at contact 1&2 thus allowing said relays BR and HR to de'e'nergize. Upon the deenergization of said relays the circuit for release magnet RM is interrupted allowing the said magnet to dei ncrgize and retract its armature. Switch C and its associated mechanisms are now at normal.

Returning now to main release relay MRR. Upon its decnergization, as previously described, the circuit for magnet CCll of line switch B is interrupted at Contact 135 of relay MRR. The said magnet COR is thereupon deenergized withdrawing the retaining pawl from connection with the ratchet wheel for wipers 17. 1S and 19, thus allowing the said wipers to be restored to normal as previously described. Upon (le energization of magnet COR, the connection between switch springs 13 is interrupted,

again restored to normal as described in connection with Fig. 2. Also, upon restoration of Wipers 17, 18, and 19 to normal, switch springs 12 and off normal springs ON are restored to normal as previously described in connection with the switch of Fig. 2. Line switch B and its associated mechanism having been restored to normal, it is available for again extending the line of sub-station A to an idle first selector upon initiation of another call.

To release the connector switch D, the receiver at sub-station E is replaced upon its switch hook. said receiver the circuit for control relay CR which was previously described as extending over the line limbs and through the sub-station E is interrupted. The said relay OR is thereupon deenergized establishing an energizing circuit for release relay RR traced from ground through winding of said relay RR, the left spring contact of switch PON I along conductor 186, through alternate contact 17 9, normal contact 178, through resistance 187 to battery. Release relay RR is thereupon energized and interrupts at its normal contact 153, the locking circuit for switch relay SlV, relay 156 and talking control relay TC, allowing said relays to deenergize. Upon deenergization of relay TC the wipers 30, and 31-are disconnected from the talking strands thus preventing any interference with any existing connections while the said wipers are wiping back over the bank contacts of the group in restoring. Upon deenergization of relay 156 the series energizing circuit for ringing control relay RCR and cut-ofi? relay COR is interrupted at contact 162 allowing the said relays to deenergize.

Returning now to the release relay RR. Upon its said energization a circuit for release magnet RM is established from ground through alternate contact 153 of relay RR and through the winding of release magnet RM to battery. The release magnet RM is thereupon energized withdrawing the retaining pawls and allowing the wipers 29, 30 and 31 to restore to normal. While the wipers are restoring it is necessary to maintain the release magnet energized and therefore a locking circuit for release relay RR is established upon its energization, the said locking circuit being traced from battery through resistance 187 and alternate contact 188 to conductor 186 and back through contact 189 and the winding of release relay RR to ground. Upon the restoration of the wipers to normal, primary oil-normal switch PON is restored to its normal position interrupting at contact 189 the locking circuit for release relay RR allowing said relay to restore and interrupt the circuit of release magnet RM. The sec ondary 013? -normal switch SON having Upon the restoration of the been restored to normal upon restoration of the wipers 29, 30, and 31 from their secondary movement, the switch D and its associated mechanism is now at normal and available for further use in establishing other connections.

Called Zine busye will assume now that the calling subscriber has extended his line circuit through first selector C and connector D to the terminals 32, 33 and 3A of the line of the called for subscriber at E and that the said called line is busy.

It will be remembered that after wipers 29, 30, and 31 connected to the line terminals 32, 33, 31 respectively, a'last secondary impulse was'transmitted over the secondary conductor energizing secondary relay SR of connector D and thereby connecting test re-- lay TR through alternate contact 161 of relay SR to the private wiper 29. The line of the called subscriber at E being busy there Will be a ground connection upon contact 32, either from a first selector if the line be calling, or if it be a called line, from a connector switch, which is connected to one of the multiple contact sets 32, 33, 34:. Thereforethe contact 32 being grounded, a circuit for test relay TR is established from the said ground at contact 32 back over wiper 29 through alternate contact 161, contact 160 and the winding of said relay TR to battery. The relay TR is thereupon energized and a locking circuit therefor is established through its locking contact 160 down over conductor 157 to ground at normal contact 153 of relay RR.

It will be remembered that upon the energization of relay SR relay 156 was energized thus interrupting the circuit for relay SR at contact 155. prevent relay SR from again restoring and connecting relay ROR to wiper 29, a looking circuit is established from ground through alternate contact 190 of test relay TR and through the winding of said relay S t to battery. Also, responsive to the energization of test relay TR a characteristic busy signal is connected to the secondary conductor S, to notify the calling subscriber that the line of the called subscriber is busy. Thus busy signal may be traced from busy back BB, through alternate contact 191 to secondary talking conductor S. back along the same conductor and out over limb 10, through the receiver of the calling subscriber at A back over the limb 11 and along the primary talking conductor I through the winding of relay IR at first selector C to ground. The subscriber at A receiving the busy signal, may by replacing his receiver upon his switch hook, restore the switches which were used in establishing this connection to normal.

Assuming that the calling subscriber replaces his receiver upon its switch hook, the

Therefore, to

circuit for relays IR and IR at first selector C is interrupted as previously described. Responsive to the interruption of the said circuit, the relays IR and IR are deenergized thus restoring first selector C and line switch B to normal as previously described. But in this case the connector switch is also restored by the calling subscriber, this being accomplished bv the battery impulse which was transmitted from alternate contact HG of relay HR, to wiper 23, bank contact 26, resistance 192 then downward through alternate contact 189 of switch POE? through the winding of release relay HR to ground. The release relay RF. is thereupon energized establishing a locking circuit and also establishing an energizing circuit for release magnet RM as previously described. Also, responsive to energization of relay BR the locking circuits for relay 156, switch relay Sil test relay TR, and talking control relay TC, are interrupted, allowing the said relays to restore. Upon deenergization of test relay TR, the energizing circuit for second ary relay SR is interrupted at contact 190, allowing said relay to deenergize. The release magnet RM having been energized the switch is restored as previously described and all of the relays having been deenergized, switch D and its associated mechanism are now at normal and available for another connectic Should a subscriber, attcr starting a call, desire not to complete it, by replacing his receiver upon its switch hook, all of the switch mechanism which had been operated up to this time would be restored. Should the subscriber at A simply remove his re ceiver from its switch hook and imme diately replace it, line switch B would connect with an idle first selector C, and relays IR and IE not finding a circuit over the line limbs, would again restore thus interrupting the circuit for magnet COR as previously described. Should a calling subscriber operate a first selector C, and then replace his receiver upon its switch hook, relays IR and IR would deenergize thus interrupting the circuit for magnet COR and establish an energizing circuit for releas relay RR, thereby restoring switch C and line switch B as previously described. Should a subscriber extend his line circuit to connector switch D and then operate the said connector switch, he may then, by replacing his receiver upon its switch hook, release all of the switches.

Line switch B of Fig. 8 illustrates diagrammatically a modification of the line switch B of Fig. 1. The said switch 13 is adapted to operate in connection with first selector C and connector switch D of Fig. l. The different controlling magnets and mechanism of line switch B have reference numerals to correspond with the corresponding parts of lin switch B but the reference numerals of switch B have the sutlix 2 added. The operation of the switch is somewhat different than the line switch of Fig. 1 being illustrated in Fig. 9.

Line switch Fig. 9 illustrates a preferred mechanical ar 'angement of switch mechanism adapted to operate in connection with the circuit arrangement 01 line switch B The corresponding parts, or parts having substantially the same functions in the switches of Fig. 2, and Fig. 9 have the same reference characters but in Fig. 9 the reference characters have the suliix 2 added. The switch of Fig. 9 operates differently from that of the switch of Fig. 2 in that the wipers when being released, are advanced to a normal position instead of being restored by a spring, as are the wipers of switch Fig. 2. In Fig. 9 motor magnet MM operates the same as motor magnet MM. iper shaft 88 is journaled in frame 35 and bracket 39 and by means of ratchet wheel i0 is adapted to be rotated to advance the wipers along the bank of contacts. Contact bank 36 is different than contact bank 36 and comprises a pair of clamping plates 37 holding ten sets of contacts 20 21 and 22 Each row of contacts has a plate 197 arranged in parallel with the row of contacts and insulated therefrom. There are three such plates 19?, one for each row of contacts in the bank, each plate having a terminal 17 18 or 19 The plate 197 having terminal 19 is arranged below and insulated from the top row of contacts 22 the plate 197 having terminal 17 is the plate of the middle row of contacts and the plate 197 having terminals 18 is the plate of the lower row of contacts 21 There are three sets of wipers 19 mounted on shaft 38 one set for each row of bank contacts. Each wiper set comprises two plates in contact and having four projecting arms, the upper part of each arm 19 being adapted to engage its bank contacts and its lower arm being adapted to engage the corresponding plate 197. Thus when a wiper 19 is advanced into engagement with a bank contact the upper and lower arm electrically connect the engaged contact with its plate 197 through the connecting wipers. Thus it will be seen that the trunks leading to the first selectors are connected to bank contacts 20 21 and 22 while the talking conductors and private conductor leading from the subscribers line, are connected to terminals 17 18 and 19 of the plates 197 so in this switch the wipers simply act to connect the bank contacts 20 21 and 22 to their plates 197. The pivoted member 48 is held against an off-normal stud 411 due to the action of off normal spring 0N pressing against its bottom inclined surface, and'also due to release catch 52 resting against its upper arm. When ratchet wheel 40 is moved off normal the stud 4:1 engaging member 48 moves away from and out of engagement with member 48 thus allowing off normal spring ON to assume an alternate position due to the upper spring ON moving upward, thereby moving the lower arm of member 48 toward he left. Spring member has an opening 55 which is adapted to hook over the end of pivoted arm 53 when magnet COR is energized, thereby allowing springs 12 to assume an alternate position. On retraction of armature 50 release catch 52 is moved toward the left and the vertical arm of member 53 is moved. thereby, this moving switch springs 13 to their alternate position. To again lift catch 52 out of engagement with arm 53, the wiper shaft 38 is rotated by motor magnet MM until the next stud 41 engages the lower lefthand projection of member 48 moving the lower arm of member 48 toward the right, thereby causing the upper arm of said member 48 to engage catch 52 lifting it out of engagement with pivoted member 53 and allowing springs 13 and'12 to again assume their normal position. At this time the wipers are in a position corresponding to that shown in Fig. 9 and magnet MM being disconnected by action of springs 13 the switch wipers remain in this position until initiation of an other call.

Operation of system including Zine switch Fig. 8.-The line switch B of Fig. 8, as previously stated, is adapted to operate'in con nection with first selector 0 and connector switch D," the operation being as follows: Assuming a subscriber at the sub-station A desires a connection with another subscriber he will remove his receiverfrom its switch hook, thereby establishing an energizing circuit for line relay LR traced from ground at normal contact 120 out over the line limbs and through sub-station A back over normal contact 121 contact 0N winding of relay, LE to battery. Line relay LR is thereby energized, closing an energizing circuit for motor magnet MM which steps the wipers forward into engagement with the first set of contacts, thus connecting line switch B with terminals 20, 21 and 22 leading to a first selector C. If the first first-selector switch of the group isbusy, there will be ground upon contact 20, and line relay LR remains energized over a locking circuit es tablished from the said ground, motor magnet. MH advancingthe wipers to the next set of contacts. If the second set of contacts lead to a busy first selector switclnline relay LE remains energized and magnet MM continues to advance the wipers until terminals 20, 21 and 22 of an idle firstselector switch are connected with.

Aspreyiously stated, an idle first selector switch has no ground or busy connection to its private terminal 20 and therefore line relay LE deenergizers, interrupting the energizing circuit for motor magnet MM Upon de'e'nergization of line relay LE an energizing circuit for impulse relay LR is 125 magnet COR is energized over a path I from ground at contact 132 of said relay 125, as previously described thus energizing the said magnet COR? Upon complete energization of magnet COR contact spring 12 is moved to its alternate position, the a said spring 12 remaining in its alternate position until the wipers of switch B have been restored to a normal position. The calling subscriber at A desiring to extend his line to a called for subscriber, operates calling device 7 the proper number of times as previously described, thereby operating a first selector C and connecting switch D to connect with the called for line.

The operation of the first selector switch C and connector switch D in this instance is the same as previously described. After the subscribers have finished conversation the called for subscriber may, by replacing his receiver upon its switch hook restore con nector switch Das previously described, and the calling subscriber, by replacing his receiver upon its switch hook, interrupts the circuit of relays IR and IR, thus causing the restoration of first'seleetor switch C as previously described. Upon the denergization of the main release relay MMR of first selector C the locking circuit for magnet COR is interrupted at contact 135, allowing the said magnet to deenergize and retract its armature. Upon deenergization of said magnet COR switch springs 13 are moved to their alternate position and an energizing circuit for relay LE is established from ground at the lower spring contact of switch 13 through the winding of relay LE to battery. On energization of relay LE a circuit is again closed through magnet MM from ground at alternate contact 122 and motor magnet MM advances the wipers until they assume a position as shown in Fig. 9. When the wipers are moved into this position, switch springs 13 are restored to normal through the operation of arm 48 and thereby interrupt the energizing circuit for relay LE which deenergizes and interrupts the energizing circuit for motor magnet MM Also upon movement of the wipers into a normal position, ofi' normal spring ON. is restored to ts normal pos onhe line switch B and its associated mechanism are now at normal and available for further use.

System including Fig. 10.The line switch B and first selector C of Fig. are adapted to operate in connection with a connector switch D of Fig. 1. As a switch structure for line switch B, I preferably employ the switch illustrated in Fig. 2 but without the use of the switch springs 12. I also provide four wipers instead of three as illustrated in switch of Fig. 2, and also four rows of bank contacts. The relays, magnets and switch contact springs of the line switch B and first selector C of Fig. 10 are indicated by reference characters corresponding to the like parts, or parts having substantially the same functions of the line switch and first selector shown in Fig. 1, but in Fig. 10 the reference characters have the sufiix In view of the general description of line switch B and first selector C of Fig. 1 it is believed a general description of line switch B and first selector C of Fig. 10 is not necessary.

Opera ion Fig. 10.Assuming a subscriber at sub-station A desires connection with another subscriber, he will remove his receiver from its switch hook, thereby establishing an energizing circuit for line relay LR over the previously described path. Line relay LE is thereby energized closing an energizing circuit through motor magnet MM and advancing wipers 17 17*, 18 and 19 into engagement with the first set of contacts 20 0 21 22 respectively, leading to a first selector switch C If this first selector switch is busy, a locking circuit for relay LR is established from ground through wiper 17 over a path as previously described, maintaining relay LR- energized and motor magnet MM therefor, advances the wipers until the terminals of an idle first selector C are connected with. As indicated at first selector switch G which is an idle switch, the private terminal 20 has no ground connection, and therefore when wiper 17 connects with contact 20 of switch C relay LE is deenergized interrupting the circuit for motor magnet MM and preventing any further advance of the wipers. Upon deenergization of relay LR an energizing circuit for relay 125 of switch C is established "from ground through normal contact 122 wiper 17*, contact 20*, normal contact 127 normal contact 128 through the winding of said relay 125 to battery. Relay 125 is thereupon energized establishing a circuit for magnet COR- from ground through alternate contact 132 normal contact of relay MRR bank contact 20 wiper 17 switch springs 13 normal contact 128 through winding of magnet COR- to bat tery, energizing the said magnet and thereby extending the line of the calling subscriber to the terminals 21 and 22 of first selector switch C Returning now to relay 125 upon its energization a circuit for relays IR and IE is established through contact 130 thereby energizing relays IR and IR*. Responsive to energization of relay IR, a circuit for relay MRR is established from ground, through contact 1% and the winding of relay MRR to battery. Relay RR is thereupon energized and by means of contact 135 a new locking circuit for magnet COR is established. Also upon energization of relay MRR the energizing circuit for relay 125 is interrupted at contact 128 allowing said relay 125 to de energize, again interrupting the initial energizing circuit for relays IR and IR' which are now maintained energized over a circuit including the line limbs and sub station as previously described.

To extend connection to a called for subscriber the calling subscriber at sub-station A now operates calling device 7 thereby interrupting the circuit for impulse relays IE and IR. The operation of relay IR interrupts the circuit for relay MMR at contact 194, but said relay MMR being sluggish it maintains its armature in an attracted position. Also responsive to the operation of relay IR, secondary relay SR is energized and being a sluggish relay maintains its armature attracted while relay IE is operating, as previously described.

Responsive to the operations of relay 1R current impulses are transmitted through primary magnet PM from ground through alternate contact 136 of relay M'RR normal contact 134?, along the upper heavily marked conductor to contact 138 of switch SON and the winding of primary magnet PM to battery. Responsive to the impulses, the primary magnet PM steps the wipers in a primary direction to the proper group, as previously described. After the last operation of relays IE and IR, secondary relay SR has its circuit interrupted long enough for it to retract its armature and a secondary impulse is thereby transmitted from ground, through normal contact 139 to normal contact 141 of switch SON, then over the previously described path, to relay BR Relay BB is thereupon energized closing a circuit through secondary magnet 3M and wipers 23 24 and 25 are now advanced to connect with an idle connector switch D as previously described. The op eration of the connector switch in connection with a called for line is as previously described.

After the subscribers have finished conversation the called for subscriber controls the release of the connector switch and the calling subscriber by replacing his receiver upon its switch hook interrupts the ener- 

